1. Field of the Invention
The invention relates generally to rotary cutting tools and, more particularly, to cutting tools, such as drills, having polycrystalline-diamond (PCD) cutting tips. The invention further relates to a method for forming a cutting tool having a polycrystalline-diamond cutting tip.
2. Background Information
Polycrystalline-diamond (PCD) drills have historically been formed as straight fluted, facet point drills. More recently, veined PCD drills have been formed having helical flutes and more complex point geometries similar to solid carbide drills. One of the major uses of such highly engineered PCD drills is for drilling in composite materials, such as carbon fiber reinforced polymer (CFRP) titanium composites.
Drilling in titanium requires good coolant flow within the drill to control the heat generated during drilling. As veined PCD drills are commonly fabricated as a PCD nib and rod which are later brazed together, it is difficult to have through-coolant holes breaking out in the flank of the drill. Typically, coolant holes are formed in the PCD nib an EDM process (electric discharge machining) that is carried out after the nib has been brazed to the rod. Such EDM process is typically quite expensive due to necessary set-up and processing times. Additionally, known veined PCD drills commonly utilize a central coolant hole through the core of the drill which feeds the coolant holes formed in the nib via EDM. The presence of such a central coolant hole generally reduces the strength, and thus the durability of the drill, a critical aspect for drills used to drill titanium materials.
There is, therefore, room for improvement in cutting tools used for drilling CFRP-titanium, particularly in the manner coolant is supplied in such drills.